Port Macquarie Coastal Geotrail Glossary Credits Plate tectonics Accretionary wedge is a mass of sediments and rock Authors: Ron Boyd & Robin Offler Schematic diagram showing movement of oceanic crust away from the mid-ocean ridge and down the subduction zone fragments that accumulates where one of Earth’s plates slides Editing: Simone Meakin Rocks of the Port Macquarie area tell the story of The geotrail under another, at a subduction zone. plate tectonics – how Earth’s crust is formed and how Figures: Kate Holdsworth To follow the Port Macquarie Coastal Geotrail, you Asthenosphere is the upper layer of Earth’s mantle, directly it moves. This geotrail spans the equivalent of up to Cartography: Stewart Watson can either travel in the same direction as the oceanic below the lithosphere, at depths of about 80–200 km. This 6000 km across the Pacific Ocean of today, in just Layout: Carson Cox plate was moving, from Shelly Beach and Sea Acres layer is highly viscous and deforms in a ductile manner. 4 km from Shelly Beach to Rocky Beach! Some rocks Photos: Guy Fleming and authors back to Rocky Beach and Town Beach, or you can do Blueschist is a metamorphic rock characterised by a blue, are made of microscopic marine organisms, others it in reverse. You can walk 4 km one way along the sodium-rich amphibole called glaucophane. Acknowledgements: David Och is thanked for allowing by volcanoes or underwater gravity currents. Some access to his research and photographs. Port Macquarie– geotrail, using the map to guide you. Alternatively you Clast is a rock fragment or grain resulting from the breakdown rocks formed at high pressures and temperatures, Hastings Council supplied a map, which has been modified. can drive to each stop, as they are all accessible from of larger rocks. over 100 km below Earth’s surface, and were later nearby car parks, or catch the local bus to/from Sea Conodonts are microfossils known from the Late Cambrian to © State of NSW through Department of Planning & brought to the surface by faulting. Acres Rainforest Centre. the Late Triassic. They are hard parts of an extinct group of Environment, 2018. Information in this publication is based animals believed to be distantly related to the living hagfish. Plate tectonics on knowledge and understanding at the time of writing and Timescale of major geological events Continental Eclogite is a metamorphic rock consisting of pyroxene may not be accurate, current or complete. The theory of plate tectonics is the most important in the region volcanic arc and garnet. underlying concept in geology. A network of rigid Metamorphism is the process by which rocks are physically or plates extends over Earth’s surface, to depths of Era Period Age* Geological activity chemically transformed by heat, pressure or fluids. Learn more about 100 km. The plates move relative to each Cenozoic Quaternary Today Modern beaches, estuaries Phacoid is an ellipsoidal, doubly tapered, deformed clast, other, forming and diverging at mid-ocean ridges, to 0.01 and dunes form which may have asymmetric shape. converging and, in places, being subducted at ocean Neogene to 23 and Volcanic events inland Serpentinite is a metamorphic rock composed of one or more Paleogene 24 NSW trenches. serpentine group minerals. GeoTours Mesozoic Cretaceous 72 to Seafloor spreading in the Turbidite is a sedimentary deposit of layers of particles that An oceanic crustal plate is formed at a mid-ocean 84 Tasman Sea spreading ridge and consists of mantle rocks in the grade upward from coarse to fine sizes and were deposited by Cretaceous to 110 to Sediment accumulates in the Trench turbidity currents in the ocean. lithosphere and asthenosphere, overlain by basalt Triassic 250 Surat and Clarence–Moreton Mid-ocean ridge Download our (Stop 1) from underwater volcanoes. As the plate basins Turbidity current is an underwater current of usually rapidly free app! Explore Clastic moving, sediment-laden water moving down a slope. migrates away from the mid-ocean ridge, the basalt Mesozoic to Triassic to 237 to Coal and sedimentation in Continental crust the geotrail at Palaeozoic Permian 295 the Sydney–Gunnedah Basin sediments Accretionary Volcanic arc is a curved chain of volcanoes formed in a tectonic collects sediment on top. At first the sediment wedge your own pace, 254 Inland volcanic activity plate above a subducting plate. If offshore, it is called a with a tour guide consists mainly of microscopic marine organisms volcanic island arc. such as radiolaria, that live near the ocean surface Triassic to 201 to Inland sedimentation and at your fingertips. Carboniferous 359 granites intrude the region and fall to the seafloor to accumulate when they die E Reference Palaeozoic Permian to 260 to Marine and inland N t (Stop 2). As the oceanic plate approaches a trench O us Silurian 425 sedimentation, with rt cr Och DJ, Leitch EC & Caprarelli G, 2007. Geological units of the it also collects sediments that flow down into the volcanic activity he Z n C ea Port Macquarie–Tacking Point tract, north-eastern Port Macquarie Mantle N c Mantle trench from nearby volcanoes (Stop 3). On reaching Ordovician to 460 to Subduction zone forms, t o Block, Mid North Coast of NSW. Quarterly Notes of the O al the trench, the denser ocean crust plate slides Cambrian 500 with associated marine I as Geological Survey of New South Wales 126. (or subducts) under another plate and is carried sedimentation and T B volcanic activity C www.pmhc.nsw.gov.au/coastalgeotrail deeper down into the earth. There it is subjected to U * Millions of years ago. D increasing pressure and temperature, forming new B U TAKE CARE WHEN EXPLORING COASTAL AREAS. WILDLIFE, WEATHER, rocks and minerals such as blueschist and eclogite S Scale: at least 500 km across SURF CONDITIONS AND UNSTABLE GROUND CAN POSE RISKS. (Stops 4 and 5). Cover photo: Port Macquarie coast.
Town Beach Geological map Geotrail stops Green Mound Section through one interpretation of the Ordovician subduction zone, looking northwards across several hundred metres Oxley Beach Gordon Street Tasman Sea Continental volcanic arc Wrights Laterite, and alluvial, swamp, and dune complexes Rocky Beach